The present invention is directed to substrates suitable for mounting one or more semiconductor chips. More specifically, the present invention is directed to apparatus which comprise one or more semiconductor chips mounted on a porous, electrically conductive substrate, said substrate having electrophoretically deposited thereon a coating of a polymeric material. One embodiment of the present invention is directed to an apparatus which comprises at least one semiconductor chip mounted on a substrate, said substrate comprising a porous, electrically conductive member having electrophoretically deposited thereon a coating of a polymeric material. Another embodiment of the present invention is directed to a process for preparing a substrate having at least one semiconductor chip mounted thereon, said process comprising: (a) providing a porous, electrically conductive substrate; (b) preparing a colloidal emulsion containing charged micelles of an organic material; (c) placing the substrate and a second electrode in contact with the colloidal emulsion; (d) applying an electrical field between the substrate and the second electrode, thereby electrophoretically depositing a polymeric coating of the organic material on the substrate; and (e) permanently mounting at least one semiconductor chip on the coated substrate. Yet another embodiment of the present invention is directed to a thermal ink jet printer for ejecting a recording liquid onto a recording medium, said printer comprising a printhead which comprises at least a channel for holding the recording liquid, at least one nozzle for ejecting the recording liquid onto the recording medium, and a heating element situated so as to enable selective heating of the ink in the channel, thereby causing ink in the channel to be ejected from the nozzle, said printhead being permanently mounted on a porous, electrically conductive substrate, said substrate having electrophoretically deposited thereon a coating of a polymeric material.
Image sensors for scanning document images, such as charge coupled devices, typically have a row or linear array of photosites together with suitable supporting circuitry integrated onto a silicon chip. Usually, a sensor is used to scan line by line across the width of a document with the document being moved or stepped lengthwise in synchronism therewith. A typical architecture for such a sensor array is given, for example, in U.S. Pat. No. 5,153,421. In a scanning system, the image resolution is proportional to the ratio of the scan width and the number of array photosites. Because of the difficulty in economically designing and fabricating an array of photosites comparable in length to the width of an image, optical reduction of the scan line to a length considerably shorter than the actual width of the image is fairly common in scanners and facsimile machines currently available. Because of the optical reduction, image resolution typically available today is relatively low when used to scan a full line. A long or full-width array having a length equal to or larger than the document line and with a large packing of co-linear photosites to assure high resolution has been and remains a very desirable aim. In the pursuit of a long or full-width array, forming the array by assembling several small chips together end to end has often been postulated. Semiconductor chips for applications other than charge coupled devices are also frequently mounted on substrates; such applications include, but are not limited to, other types of photosensitive semiconductor chips, light-emitting diode print bars, chips related to thermal ink jet technology, or the like.
Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
Since drop-on-demand systems require no ink recovery, charging, or deflection, the system is much simpler than the continuous stream type. There are different types of drop-on-demand ink jet systems. One type of drop-on-demand system has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. The relatively large size of the transducer prevents close spacing of the nozzles, and physical limitations of the transducer result in low ink drop velocity. Low drop velocity seriously diminishes tolerances for drop velocity variation and directionality, thus impacting the system's ability to produce high quality copies. Drop-on-demand systems which use piezoelectric devices to expel the droplets also suffer the disadvantage of a slow printing speed.
The other type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets and allows very close spacing of nozzles. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to vaporize almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. When the channel refills and the hydrodynamic motion of the ink substantially stops, the process is ready to start all over again. With the introduction of a droplet ejection system based upon thermally generated bubbles, commonly referred to as the "bubble jet" system, the drop-on-demand ink jet printers provide simpler, lower cost devices than their continuous stream counterparts, and yet have substantially the same high speed printing capability.
The operating sequence of the bubble jet system begins with a current pulse through the resistive layer in the ink filled channel, the resistive layer being in close proximity to the orifice or nozzle for that channel. Heat is transferred from the resistor to the ink. The ink becomes superheated far above its normal boiling point, and for water based ink, finally reaches the critical temperature for bubble formation or nucleation of around 280.degree. C. Once nucleated, the bubble or water vapor thermally isolates the ink from the heater and no further heat can be applied to the ink. This bubble expands until all the heat stored in the ink in excess of the normal boiling point diffuses away or is used to convert liquid to vapor, which removes heat due to heat of vaporization. The expansion of the bubble forces a droplet of ink out of the nozzle, and once the excess heat is removed, the bubble collapses. At this point, the resistor is no longer being heated because the current pulse has passed and, concurrently with the bubble collapse, the droplet is propelled at a high rate of speed in a direction towards a recording medium. The surface of the printhead at or near the resistor encounters a severe cavitational force by the collapse of the bubble, which tends to erode it. Subsequently, the ink channel refills by capillary action. This entire bubble formation and collapse sequence occurs in about 10 microseconds. The channel can be refired after 50 to 500 microseconds minimum dwell time to enable the channel to be refilled and to enable the dynamic refilling factors to become somewhat dampened. Thermal ink jet equipment and processes are well known and are described in, for example, U.S. Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899, U.S. Pat. No. 4,412,224, U.S. Pat. No. 4,532,530, and U.S. Pat. No. 4,774,530, the disclosures of each of which are totally incorporated herein by reference.
In ink jet printing, a printhead is usually provided having one or more ink-filled channels communicating with an ink supply chamber at one end and having an opening at the opposite end, referred to as a nozzle. These printheads form images on a recording medium such as paper by expelling droplets of ink from the nozzles onto the recording medium. The ink forms a meniscus at each nozzle prior to being expelled in the form of a droplet. After a droplet is expelled, additional ink surges to the nozzle to reform the meniscus.
In thermal ink jet printing, a thermal energy generator, usually a resistor, is located in the channels near the nozzles a predetermined distance therefrom. The resistors are individually addressed with a current pulse to momentarily vaporize the ink and form a bubble which expels an ink droplet. As the bubble grows, the ink bulges from the nozzle and is contained by the surface tension of the ink as a meniscus. The rapidly expanding vapor bubble pushes the column of ink filling the channel towards the nozzle. At the end of the current pulse the heater rapidly cools and the vapor bubble begins to collapse. However, because of inertia, most of the column of ink that received an impulse from the exploding bubble continues its forward motion and is ejected from the nozzle as an ink drop. As the bubble begins to collapse, the ink still in the channel between the nozzle and bubble starts to move towards the collapsing bubble, causing a volumetric contraction of the ink at the nozzle and resulting in the separation of the bulging ink as a droplet. The acceleration of the ink out of the nozzle while the bubble is growing provides the momentum and velocity of the droplet in a substantially straight line direction towards a recording medium, such as paper. The printhead is typically mounted on a substrate, which preferably functions as a heat sink.
There are two general configurations for thermal drop-on-demand ink jet printheads. In one configuration, droplets are propelled from nozzles in a direction parallel to the flow of ink in ink channels and parallel to the surface of the bubble-generating heating elements of the printhead, such as, for example, the printhead configuration disclosed in U.S. Pat. No. Re. 32,572, the disclosure of which is totally incorporated herein by reference. This configuration is sometimes referred to as an edge shooter or a side shooter. The other thermal ink jet configuration propels droplets from nozzles in a direction normal to the surface of the bubble-generating heating elements, such as, for example, the printhead disclosed in U.S. Pat. No. 4,568,953, the disclosure of which is totally incorporated herein by reference. This configuration is sometimes referred to as a roofshooter. A fundamental difference between the two configurations lies in the direction of droplet ejection, in that the side shooter configuration ejects droplets in the plane of the substrate having the heating elements, whereas the roofshooter ejects droplets out of the plane of the substrate having the heating elements and in a direction normal thereto.
Thermal ink jet printheads can be used in carriage-type printers for printing swaths of information and then stepping the recording medium a distance of one swath and continuing to print adjacent swaths of information until a full page has been printed. Alternatively, the printheads can be assembled as subunits of a partial or full page width printhead and arranged on a structural imaging bar for printing. In page width printing, the printheads may be assembled by abutting a plurality of the printhead subunits end-to-end on the image bar or by staggering them on two separate image bars or on opposite sides of the same image bar. The fabrication approaches for making either large array or pagewidth thermal ink jet printheads generally fall into two categories, namely monolithic approaches, in which one or both of the printhead components (heater plate and channel plate) are a single large array of page width size, and subunit approaches, in which smaller subunits are combined to form the large array or page width print bar. The subunit approach tends to result in a higher yield of usable subunits if they can be aligned precisely with respect to each other.
U.S. Pat. No. 5,160,945 (Drake), the disclosure of which is totally incorporated herein by reference, discloses a page width thermal ink jet printhead of the type assembled from fully functional roofshooter type printhead subunits fixedly mounted on the surface of one side of a structural bar. A passageway is formed adjacent to the bar side surface containing the printhead subunits with openings provided between the passageway and the ink inlets of the printhead subunits mounted thereon, so that ink supplied to the passageway in the bar will maintain the individual subunits full of ink. The size of the printing zone for color printing is minimized because the roofshooter printhead subunits are mounted on one edge of the structural bar and may be stacked one on top of the other without need to provide space for the printhead subunits and/or ink supply lines. In addition, the structural bar thickness enables the bar to be massive enough to prevent warping because of printhead operating temperatures.
U.S. Pat. No. 5,192,959 (Drake et al.), the disclosure of which is totally incorporated herein by reference, discloses a mechanism for accurately mounting a large area semiconductive device within a larger system. The semiconductive device, formed by the linear abutment of semiconductive subunits divided from a larger semiconductive wafer, must be accurately positioned to enable the operation of which it was intended. In one embodiment, the subunits are thermal ink jet arrays which are abutted to form a page width printhead. The semiconductive device includes a reference plate or substrate having a generally planar surface for mounting an array of functional subunits thereon. The semiconductive device further includes two or more individual subunits which are also affixed to the planar surface, thereby forming alignment pads for the assembled semiconductive device. When incorporated into the system, the alignment pads are received by frame members or alignment points to provide positive alignment of the reference plate and the attached array of subunits within the system.
U.S. Pat. No. 5,272,113 (Quinn), the disclosure of which is totally incorporated herein by reference, discloses semiconductor chips, such as photosensor arrays in a full-width scanner, which are mounted on a substrate to maintain reasonably consistent spacing among chips regardless of temperature conditions during use. After chips are tacked onto the substrate with uncured epoxy, the assembly is brought to a low temperature prior to the heating of the curing step. The technique permits design of the assembly to compensate for differences between the thermal coefficient of expansion of the chips and that of the substrate, while also minimizing mechanical stresses on the chips caused by heating in the course of use.
Additional examples of large array or page width thermal ink jet printheads are disclosed in, for example, U.S. Pat. No. 4,985,710, U.S. Pat. No. 4,935,750, U.S. Pat. No. 4,851,371, U.S. Pat. No. 4,829,324, U.S. Pat. No. 4,822,755, U.S. Pat. No. 4,712,018, U.S. Pat. No. 4,690,391, and U.S. Pat. No. 4,463,359, the disclosures of each of which are totally incorporated herein by reference.
U.S. Pat. No. 4,642,170 (Alvino et al.), the disclosure of which is totally incorporated herein by reference, discloses a method of electrophoretically depositing a coating of polysulfones or polyethersulfones on a conductive substrate. An amine-free solution is formed in an organic solvent of the polysulfones or polyethersulfones. An emulsion is formed by combining the solution with an organic non-solvent for the polymer which contains up to about 0.6 parts by weight of an organic nitrogen containing base per parts by weight of the polymer. A direct current is applied between a conductive substrate and the emulsion which results in the deposition of the polymer on the substrate.
U.S. Pat. No. 4,425,467 (Alvino et al.), the disclosure of which is totally incorporated herein by reference, discloses a method of making a nonaqueous emulsion from which a polymer can be electrodeposited. A mixture is prepared of about 50 to about 150 parts by weight of a nonaqueous organic, nonelectrolizable, nonsolvent for the polymer with about 0.8 to about 1.2 parts by weight of a nitrogen-containing base which can be a tertiary amine, an imidazole, or mixture of a tertiary amine and an imidazole. To the mixture is added a solution of 1 part by weight of the polymer which can be a polyamic acid, a polyamide imide, a polyimide, a polyparabanic acid, a polysulfone, or a mixture of these polymers. The polymer is in a nonaqueous, organic, nonelectrolizable aprotic solvent such as N-methyl-2-pyrrolidone.
U.S. Pat. No. 4,533,448 (Scala et al.), the disclosure of which is totally incorporated herein by reference, discloses an electrodepositable emulsion which comprises a soluble un-ionized polymer containing an amic acid or amide linking group, a non-electrolyzable organic solvent for the polymer and a nonelectrolyzable organic nonsolvent for the polymer. The weight ratio of the solvent to the nonsolvent is about 0.1 to about 0.5 and the polymer is about 0.4 to about 5 percent by weight of the weight of the solvent. No amine or surface active agent is used. A workpiece is coated with the polymer by placing it into the emulsion about one-half to about two inches away from the cathode. Constant dc voltage is applied between the cathode and the workpiece until a coating of a desired thickness has been deposited on the workpiece. The workpiece is then removed, dried, and cured.
U.S. Pat. No. 4,391,933 (Scala et al.), the disclosure of which is totally incorporated herein by reference, discloses an emulsion which comprises about 8 to about 20 percent of a solvent, about 0.5 to 5 percent of an epoxy resin dissolved in the solvent to form a discontinuous phase, about 75 to about 90 percent of a precipitant as the continuous phase, and an emulsifier in an amount sufficient to react stoichiometrically with the epoxy and hydroxyl groups on the epoxy resin up to about 900% in excess of stoichiometric. A conductive workpiece is placed in the emulsion about 1/2 to about 2 inches from an electrode which is also immersed in the emulsion. A direct electric current potential is applied between the workpiece and the electrode with the workpiece as the anode. About 50 to about 400 volts and about 2 to about 50 milliamperes are used until a coating of the desired thickness has been deposited on the workpiece. The solvent and precipitant are preferably ketones such as cyclohexanone, and methylethylketone or isobutylketone, respectively. The epoxy resin is preferably a bisphenol A epoxy resin having an average molecular weight of about 2000 to about 15,000. The emulsifier is preferably an amine.
Copending application U.S. Ser. No. 08/705,914, filed Aug. 29,1996 now abandoned, entitled "Thermal Ink Jet Printhead With Ink Resistant Heat Sink Coating," with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a heat sink for a thermal ink jet printhead having improved resistance to the corrosive effects of ink by coating the surface of the heat sink with an ink resistant film formed by electrophoretically depositing a polymeric material on the heat sink surface. In one described embodiment, a thermal ink jet printhead is formed by bonding together a channel plate and a heater plate. Resistors and electrical connections are formed in the surface of the heater plate. The heater plate is bonded to a heat sink comprising a zinc substrate having an electrophoretically deposited polymeric film coating. The film coating provides resistance to the corrosion of higher pH inks. In another embodiment, the coating has conductive fillers dispersed therethrough to enhance the thermal conductivity of the heat sink. In one embodiment, the polymeric material is selected from the group consisting of polyethersulfones, polysulfones, polyamides, polyimides, polyamide-imides, epoxy resins, polyetherimides, polyarylene ether ketones, chloromethylated polyarylene ether ketones, acryloylated polyarylene ether ketones, polystyrene and mixtures thereof.
Copending application U.S. Ser. No. 08/703,138, filed Aug. 29, 1996 now U.S. Pat. No. 5,843,325, filed concurrently herewith, entitled "Method for Applying an Adhesive Layer to a Substrate Surface," with the named inventors Ram S. Narang, Stephen F. Pond, and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a method for uniformly coating portions of the surface of a substrate which is to be bonded to another substrate. In a described embodiment, the two substrates are channel plates and heater plates which, when bonded together, form a thermal ink jet printhead. The adhesive layer is electrophoretically deposited over a conductive pattern which has been formed on the binding substrate surface. The conductive pattern forms an electrode and is placed in an electrophoretic bath comprising a colloidal emulsion of a preselected polymer adhesive. The other electrode is a metal container in which the solution is placed or a conductive mesh placed within the container. The electrodes are connected across a voltage source and a field is applied. The substrate is placed in contact with the solution, and a small current flow is carefully controlled to create an extremely uniform thin deposition of charged adhesive micelles on the surface of the conductive pattern. The substrate is then removed and can be bonded to a second substrate and cured. In one embodiment, the polymer adhesive is selected from the group consisting of polyamides, polyimides, polyamide-imides, epoxy resins, polyetherimides, polysulfones, polyether sulfones, polyarylene ether ketones, polystyrenes, chloromethyloted polyarylene ether ketones, acryloylated plyarylene ether ketones, and mixtures thereof.
Copending application U.S. Ser. No. 08/697,750, filed Aug. 29, 1996, filed concurrently herewith, entitled "Electrophoretically Deposited Coating For the Front Face of an Ink Jet Printhead," with the named inventors Ram S. Narang, Stephen F. Pond, and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses an electrophoretic deposition technique for improving the hydrophobicity of a metal surface, in one embodiment, the front face of a thermal ink jet printhead. For this example, a thin metal layer is first deposited on the front face. The front face is then lowered into a colloidal bath formed by a fluorocarbon-doped organic system dissolved in a solvent and then dispersed in a non-solvent. An electric field is created and a small amount of current through the bath causes negatively charged particles to be deposited on the surface of the metal coating. By controlling the deposition time and current strength, a very uniform coating of the fluorocarbon compound is formed on the metal coating. The electrophoretic coating process is conducted at room temperature and enables a precisely controlled deposition which is limited only to the front face without intrusion into the front face orifices. In one embodiment, the organic compound is selected from the group consisting of polyimides, polyamides, polyamide-imides, polysulfones, polyarylene ether ketones, polyethersulfones, polytetrafluoroethylenes, polyvinylidene fluorides, polyhexafluoro-propylenes, epoxies, polypentafluorostyrenes, polystyrenes, copolymers thereof, terpolymers thereof, and mixtures thereof.
Copending application U.S. Ser. No. 08/705,375, filed Aug. 29, 1996, filed concurrently herewith, entitled "Improved Curable Compositions," with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Ralph A. Mosher, the disclosure of which is totally incorporated herein by reference, discloses an improved composition comprising a photopatternable polymer containing at least some monomer repeat units with photosensitivity-imparting substituents, said photopatternable polymer being of the general formula ##STR1## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR2## B is one of several specified groups, such as ##STR3## or mixtures thereof, and n is an integer representing the number of repeating monomer units. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymer and a thermal ink jet printhead containing therein a layer of a crosslinked or chain extended polymer of the above formula.
Copending application U.S. Ser. No. 08/705,365, filed Aug. 29, 1996 now U.S. Pat. No. 5,849,809, filed concurrently herewith, entitled "Hydroxyalkylated High Performance Curable Polymers," with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a composition which comprises (a) a polymer containing at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula ##STR4## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR5## B is one of several specified groups, such as ##STR6## or mixtures thereof, and n is an integer representing the number of repeating monomer units, wherein said photosensitivity-imparting substituents are hydroxyalkyl groups; (b) at least one member selected from the group consisting of photoinitiators and sensitizers; and (c) an optional solvent. Also disclosed are processes for preparing the above polymers and methods of preparing thermal ink jet printheads containing the above polymers.
Copending application U.S. Ser. No. 08/705,488, filed Aug. 29, 1996 filed concurrently herewith, entitled "Improved High Performance Polymer Compositions," with the named inventors Thomas W. Smith, Timothy J. Fuller, Ram S. Narang, and David J. Luca, the disclosure of which is totally incorporated herein by reference, discloses a composition comprising a polymer with a weight average molecular weight of from about 1,000 to about 65,000, said polymer containing at least some monomer repeat units with a first, photosensitivity-imparting substituent which enables crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer also containing a second, thermal sensitivity-imparting substituent which enables further polymerization of the polymer upon exposure to temperatures of about 140.degree. C. and higher, wherein the first substituent is not the same as the second substituent, said polymer being selected from the group consisting of polysulfones, polyphenylenes, polyether sulfones, polyimides, polyamide imides, polyarylene ethers, polyphenylene sulfides, polyarylene ether ketones, phenoxy resins, polycarbonates, polyether imides, polyquinoxalines, polyquinolines, polybenzimidazoles, polybenzoxazoles, polybenzothiazoles, polyoxadiazoles, copolymers thereof, and mixtures thereof.
Copending application U.S. Ser. No. 08/697,761, filed Aug. 29, 1996 now U.S. Pat. No. 5,889,077, filed concurrently herewith, entitled "Process for Direct Substitution of High Performance Polymers with Unsaturated Ester Groups," with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Raymond K. Crandall, the disclosure of which is totally incorporated herein by reference, discloses a process which comprises reacting a polymer of the general formula ##STR7## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR8## B is one of several specified groups, such as ##STR9## or mixtures thereof, and n is an integer representing the number of repeating monomer units, with (i) a formaldehyde source, and (ii) an unsaturated acid in the presence of an acid catalyst, thereby forming a curable polymer with unsaturated ester groups. Also disclosed is a process for preparing an ink jet printhead with the above polymer.
Copending application U.S. Ser. No. 08/705,463, filed Aug. 29, 1996 now U.S. Pat. No. 5,739,254, filed concurrently herewith, entitled "Process for Haloalkylation of High Performance Polymers," with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Raymond K. Crandall, the disclosure of which is totally incorporated herein by reference, discloses a process which comprises reacting a polymer of the general formula ##STR10## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR11## B is one of several specified groups, such as ##STR12## or mixtures thereof, and n is an integer representing the number of repeating monomer units, with an acetyl halide and dimethoxymethane in the presence of a halogen-containing Lewis acid catalyst and methanol, thereby forming a haloalkylated polymer. In a specific embodiment, the haloalkylated polymer is then reacted further to replace at least some of the haloalkyl groups with photosensitivity-imparting groups. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymer.
Copending application U.S. Ser. No. 08/705,479, filed Aug. 29, 1996, filed concurrently herewith, entitled "Processes for Substituting Haloalkylated Polymers With Unsaturated Ester, Ether, and Alkylcarboxymethylene Groups," with the named inventors Timothy J. Fuller, Ram S. Narang, Thomas W. Smith, David J. Luca, and Raymond K. Crandall, the disclosure of which is totally incorporated herein by reference, discloses a process which comprises reacting a haloalkylated aromatic polymer with a material selected from the group consisting of unsaturated ester salts, alkoxide salts, alkylcarboxylate salts, and mixtures thereof, thereby forming a curable polymer having functional groups corresponding to the selected salt. Another embodiment of the invention is directed to a process for preparing an ink jet printhead with the curable polymer thus prepared.
Copending application U.S. Ser. No. 08/705,376, filed Aug. 29, 1996, filed concurrently herewith, entitled "Blends Containing Curable Polymers," with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a composition which comprises a mixture of (A) a first component comprising a polymer, at least some of the monomer repeat units of which have at least one photosensitivity-imparting group thereon, said polymer having a first degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram and being of the general formula ##STR13## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR14## B is one of several specified groups, such as ##STR15## or mixtures thereof, and n is an integer representing the number of repeating monomer units, and (B) a second component which comprises either (1) a polymer having a second degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram lower than the first degree of photosensitivity-imparting group substitution, wherein said second degree of photosensitivity-imparting group substitution may be zero, wherein the mixture of the first component and the second component has a third degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram which is lower than the first degree of photosensitivity-imparting group substitution and higher than the second degree of photosensitivity-imparting group substitution, or (2) a reactive diluent having at least one photosensitivity-imparting group per molecule and having a fourth degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram, wherein the mixture of the first component and the second component has a fifth degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram which is higher than the first degree of photosensitivity-imparting group substitution and lower than the fourth degree of photosensitivity-imparting group substitution; wherein the weight average molecular weight of the mixture is from about 10,000 to about 50,000; and wherein the third or fifth degree of photosensitivity-imparting group substitution is from about 0.25 to about 2 milliequivalents of photosensitivity-imparting groups per gram of mixture. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned composition.
Copending application U.S. Ser. No. 08/705,372, filed Aug. 29, 1996, filed concurrently herewith, entitled "High Performance Curable Polymers and Processes for the Preparation Thereof," with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a composition which comprises a polymer containing at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula ##STR16## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR17## B is one of several specified groups, such as ##STR18## or mixtures thereof, and n is an integer representing the number of repeating monomer units, wherein said photosensitivity-imparting substituents are allyl ether groups, epoxy groups, or mixtures thereof. Also disclosed are a process for preparing a thermal ink jet printhead containing the aforementioned polymers and processes for preparing the aforementioned polymers.
Copending application U.S. Ser. No. 08/705,490, filed Aug. 29, 1996 now U.S. Pat. No. 5,863,963, filed concurrently herewith, entitled "Halomethylated High Performance Curable Polymers," with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a process which comprises the steps of (a) providing a polymer containing at least some monomer repeat units with halomethyl group substituents which enable crosslinking or chain extension of the polymer upon exposure to a radiation source which is electron beam radiation, x-ray radiation, or deep ultraviolet radiation, said polymer being of the formula ##STR19## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR20## B is one of several specified groups, such as ##STR21## or mixtures thereof, and n is an integer representing the number of repeating monomer units, and (b) causing the polymer to become crosslinked or chain extended through the photosensitivity-imparting groups. Also disclosed is a process for preparing a thermal ink jet printhead by the aforementioned curing process.
Copending application U.S. Ser. No. 08/697,760, filed Aug. 29, 1996, filed concurrently herewith, entitled "Aqueous Developable High Performance Curable Polymers," with the named inventors Ram S. Narang and Timothy J. Fuller, the disclosure of which is totally incorporated herein by reference, discloses a composition which comprises a polymer containing at least some monomer repeat units with water-solubility-imparting substituents and at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula ##STR22## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR23## B is one of several specified groups, such as ##STR24## or mixtures thereof, and n is an integer representing the number of repeating monomer units. In one embodiment, a single functional group imparts both photosensitivity and water solubility to the polymer. In another embodiment, a first functional group imparts photosensitivity to the polymer and a second functional group imparts water solubility to the polymer. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymers.
Substrates for mounting semiconductor chips preferably have desirable thermal conductivity characteristics, desirable thermal expansion characteristics, and desirable surface characteristic, are easily machined, and also have desirable aesthetic characteristics. For example, in a thermal ink jet printhead substrate, which preferably functions as a heat sink, it is important to have good thermal conductivity as well as the ability to form required features in the substrate at low cost. For a page width buttable printhead array, it is also important that the thermal expansion of the substrate have a good match to that of the silicon printhead die. If the substrate coefficient of thermal expansion differs too much from that of the silicon die, such as would occur if the substrate were made of aluminum, adjacent dies would push each other apart during die bond curing. Graphite is one suitable material for such substrates, and has an additional advantage in that it is readily machinable. Other examples include sintered metals, such as sintered bronze, sintered stainless steel, and the like. One disadvantage of porous materials such as graphite as the material for a printhead substrate, however, is its porosity. For example, silver-filled epoxies are sometimes used to bond the components of the printhead to the substrate because of the desirable thermal conductivity of such epoxies. When a silver-filled epoxy is used to bond the printhead components or subunits to the substrate, the resin may tend to wick into the porous substrate, leaving a silver-rich, adhesive-poor medium for adhering to the subunits. Further, on the front face of the printhead, ink can be absorbed by a porous material, thereby possibly swelling the adhesive bonds. In printing processes entailing printing with more than one color, the absorbed ink on the front face can also contaminate inks of other colors. Graphite also tends to shed particulates. In some page width buttable printhead arrays, fluid passageways in the substrate allow cooling fluid to maintain the bar temperature constant to minimize variations in spot size. When the cooling fluid is directly in contact with the graphite, over time some of the fluid may evaporate through the porous graphite. In addition, the cooling fluid can become loaded with graphite particles. Shedding of graphite particles onto the hand while handling the substrate is a further disadvantage. The shed particles can also contaminate the ink and the printing substrate (i.e., paper, transparency material, or the like).
Thus, while known compositions and processes are suitable for their intended purposes, a need remains for improved substrates for mounting semiconductor chips. There is also a need for improved heat sinking substrates for thermal ink jet printheads. A need also remains for improved thermal ink jet printhead arrays. In addition, a need remains for thermal ink jet printheads and printhead arrays having substrates with desirable thermal expansion characteristics. Further, there is a need for thermal ink jet printheads and printhead arrays having substrates with both desirable thermal expansion characteristics and desirable porosity characteristics. Additionally, there is a need for thermal ink jet printheads and printhead arrays having substrates with both desirable thermal expansion characteristics and reduced or eliminated shedding of particulates. There is also a need for thermal ink jet printheads and printhead arrays with aesthetically pleasing substrates.